1. Field of the Invention
The present invention is directed to a roll with a heat exchanger. More specifically, the present invention is directed to a roll having a heat exchanger disposed inside the roll jacket. The heat exchanger connects with a supply mechanism for inflow and outflow of an external heat transfer fluid to its primary side. A secondary side of the heat exchanger and an inner surface of the roll jacket support an internal heat transfer fluid.
2. Discussion of the Background Information
DD 225 767 A1 discloses rolls used in calenders to process paper webs or other material webs. Rolls cooperate with adjacent rolls to form nips therebetween. It is known in such arrangements that it is often preferable to heat or cool the material web, either at a nip or away from such a nip.
The need to cool the roll is not limited to situations in which only the material web needs to be cooled, but includes the roll itself; for example, when the roll has an elastic coating, heat builds up during fulling of the elastic coating, and must be dissipated to prevent damage to the coating and/or web. In other applications, the roll may need to be heated when the material web is to be exposed to an elevated pressure and/or an elevated temperature. In such cases, it is known to introduce a heat transfer fluid, for example, cooling water or heating steam, into the roll using a heat exchanger.
The above noted DD 225 767 A1 discloses a fluid path for an internal heat transfer fluid. The heat transfer fluid is present in a gas phase and in a liquid phase. It condenses on the heat exchanger and is then thrown against the inside wall of the roll jacket, where it evaporates. The resultant steam condenses when it arrives at the heat exchanger, whereupon the process repeats itself.
A drawback of such a heat exchanger is that it operates only with certain temperature differentials, and only for cooling the roll. It can also be controlled only to a limited extent.